Valve mechanism



July 27, 1954 W, H KAElTER 2,684,661

VALVE MECANISM Filed Deo. 8, 1952 2 Sheets-Sheet l IN V EN TOR:

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' TTYT July 27, 1954 w. H. KEITER VALVE MECHANISM Filed Deo. a, 1952 2 sheets-sheet 2 INVEN TOR: William H. KEL'ET.

Patented July 27, A1954 UNITED STATES PATENT OFFICE VALVE MECHANISM William H. Keiter, Toledo, Ohio Application December 8, 1952, Serial No. 324,645

11 claims. 1

This invention relates to a valve mechanism for controlling the reciprocations of an expansible chamber motor. More particularly it deals with an automatic nuid controlled vD-type valve for controlling the reciprocations of a piston in a cylinder, such as for example, a piston motor for a reciprocating type of grease pump which pump is connected to a grease gun where a constant pressure behind the gun is required at all times whether the -gun is being operated or not.

It is an object of this invention to produce a simple, eflicient, effective and economic valve mechanism for a reciprocating expansible chamber motor.

Another object is to produce an automatic iiuid controlled valve mechanism for a reciprocating expansible chamber motor which maintains a constant pressure of fluid against the piston in the reciprocating motor at all times, Whether or not the piston is continuously or intermittently operated even for a part of a stroke.

Another object is toproduce such va valve mechanism which may be readily adapted to any D-type valve controlled reciprocating expansible chamber motor without the necessity of providing a special piston or a special cylinder for the valve mechanism.

Another object is to provide such a valve mechanism which may be used for operating grease or sealing compound pumps such as used along the automobile assembly lines.

Another object is to provide a valve control mechanism for a reciprocating expansible chamber motor which does not have any exposed mechanically moving parts or cams which Will wear or which can be maladjusted by inexperienced operators.

Another object is to provide such a valve mechanism which may be'adapted to a reciprocating motor for a grease type of pump, the piston of which'motor need not be integral with the pump piston so that the motor and valve mechanism may be readily Vdisconnected from the pump, if desired, for purposes of adjustment and repair.

Another object is to provide a valve mechanism for a reciprocating eXpansible chamber motor which may be adapted for pumps having any effective motor to pump pressure ratios, such as from about 5:1 to 80` to 1, and reciprocation speeds from less than one per minute to more than one per second.

Generally speaking, the valve mechanism according to this invention is adapted to control the common type of reciprocating, sliding or D- valve employed in controlling the reciprocations of a piston in a cylinder responsive to fluid pressures. This mechanism comprises a fiuid pressure box or chest in which a fluid, such as steam or compressed air, is maintained at a constant pressure over and around a D-valve. The D- valve alternately connects one end of the cylinder to the pressure in the chest and the other end of the cylinder to the exhaust, and vice versa, as it is slid back and forth over two of three adjacent openings or ports in series along a side of the chest. The mechanism of this invention comprises a pair of control pistons mounted in the chest, one on each side of the D-valve, which control pistons are provided with pivoted arms that push against opposite ends of the D-valve to move it from one of its positions or stations to another. In order to prevent the two control pistons in the chest from simultaneously pushing against each other and deadlocking their movements, cams are provided on each of the control piston rods, which together with the action of a spring move the pivoted engaging arm of one of the control pistons out of stopping engagement .with the D-valve when the other control piston arm is in operative position and is moving or holding the D-valve in one of its positions or stations. These tWo control pistons are operated by the pressure from the main motor cylinder itself and the pressure in the chest. To

C maintain the D-valve in either one of its positions while the control pistons are changing engagement With the D-valve, an additional resilient means may be provided which operates between the chest wall and the D-valve itself.

The above mentioned and other features and objects of this invention and the manner of attaining them are given more speciiic disclosure in the following description of an embodiment of this invention taken in conjunction With the accompanying drawings, wherein:

Fig. 1 is a sectional plan view of one embodiment of the valve mechanism of this invention in a fluid pressure chest for controlling a reciprocating expansible chamber motor;

Fig. 2 is a vertical section along lines II-II of Fig. 1 showing the mechanism as it is attached to a motor having a cylinder and a reciprocating piston therein, with one position of the piston being shown in dotted lines;

Fig. 3 is a vertical section along line III- III of Fig. 2;

Fig. 4 is a similar section to Fig. 3 with part of the cylinder broken away, but showing a pivoted lever arm on a control piston ofthe valve mechanism in the chest, cammed out of engagement with the D-valve, or a vertical section along line IV--IV of Fig. 5;

Fig. 5 is a view similar to Fig. 1 showing one pivoted lever arm on one control piston in D- valve abutting position, and the other pivoted lever arm on the other control piston in disengagement with the D-valve as in Fig. 4;

Fig. 6 is similar to Fig. 5 showing the D-valve in the opposite position from that shown in Fig. 1;

Fig. 7 is a side elevation of a lubricating system including a reciprocating motor with a valve mechanism according to this invention, together with a grease pump in a reservoir or barrel and a grease gun.

I. THE DESCRIPTION OF THE APPARATUS 1. The reciprocating epunsible chamber motor Referring to Figs. 1, 2 and 3 on the rst sheet of drawings, the reciprocating expansible charnber motor to which the present valve mechanism of this invention is applied comprises by way of example a motor cylinder housing IIJ provided with a cylindrical chamber I I and a iiat machined outer surface I2 to which a chest containing the valve mechanism may be attached, and in which surface may be provided a rectangular recessed portion I4 in which the D-valve mechanism slides. Equally spaced longitudinally along the center of the bottom of the recessed portion i4 may be three ports or openings I6, Il and I8 which communicate respectively with ducts 2l, 22 and 23 in the cylinder block or housing I0. The central opening I'I may be larger than the other two openings I6 and I8, and it is continuously covered by the D-valve mechanism since it communicates through duct 22 which may be open to the atmosphere or connected to an exhaust pipe 25. In the embodiment shown, the ducts 2l and 23 from the ports I6 and I8, respectively, extend longitudinally through the housing I0 to the opposite ends of the cylinder block.

One end of the cylinder, the right end shown in the drawings, may be provided with a head plate 30 and an internal U-shaped duct 3l (see Fig. 2) which connects the end of the duct 23 to the end of the chamber II of the cylinder, thereby connecting the expansible chamber through the ducts 3| and 23 with the chest of the valve mechanism mounted on the cylinder. This head plate 30 may be fastened to the end of the cylinder by any suitable means such as bolts 32 which may be tapped into the flange 33 provided at the corresponding end of the cylinder housing I0. The other end of the cylinder housing IG may be capped by an apertured plate o1' head 35 provided with an internal U-shaped duct 36 similar to the duct 3l, which communicates with the duct 2I in the cylinder housing I5 thereby connecting the other end of the cylinder chamber II with the chest of the valve mechanism. Bolts 3l, similar to bolts 32, may be provided for attaching this head 35 to the other end of the cylinder housing IG, which bolts 31 enter into tapped holes in a flange 38, similar to the flange 33, of the cylinder housing I0. This head 35 may also be provided with outwardly extending iianges or portions 40, provided with apertures 4i by means of which anges the whole motor and valve mechanism assembly may be mounted or supported onto a suitable bracket, such as for example shown in Fig. 7. The central portion of the head 35 is provided with a cylindrical boss 45 surrounding a Central aperture 46 through which a piston rod may slide. To the end of the boss 45 may be bolted a clamping sleeve 47 for maintaining a suitable stulng or packing material 48 to form a :duid tight joint between a piston rod and the aperture 45 in the head 35.

Reciprocating in the chamber II is provided a main or motor piston 50 which may also be provided with piston rings 5I. The piston may be fastened to the end of a piston rod 52 which extends through the aperture 46 in the head 35 and is permitted to slide through the head a distance corresponding to the length of the cylinder chamber II.

2. The D-calve chest Mounted on the flat portion of the cylinder housing I0 is a valve chest 50 which may be fastened to the flat portion I2 by means of bolts such as 6I cooperating with tapped holes 62 in the flange portion 63 (see Fig. 3) of the cylinder housing I0. The chest 6l) is provided with an interior chamber 65 open at the one side which contacts the surface I2, which open side is substantially greater than the recessed portion I4 in the top of the cylinder housing It). Within the chamber 65 and slidable from end to end of the recess I4, is a D-valve I0 which is spaced below the ceiling 1I of the chamber 65 a sufficient distance to provide operative space for a resilient means l2, such as a helical compression spring which maintains the D-valve at either one end or the other end of its slide path in the recess I4. There may be provided both in the top of the D-valve 'i0 and in the surface 'II recesses 'i3 and 14, respectively, in which the ends of spring 'I2 seat. As shown in the drawing, the D-valve ID is cup-shaped with a chamber 'i5 or suflicient length and depth for connecting the two of the ports It and Il or I'I and I8 and not all three of said ports. The length of the D-valve 'IG is thus shorter than the recess I4 but of the same width so that the D-valve may slide from one end to the other of the recess I4 and at either end it will expose to the chamber 65 of the chest 6G, either one or the other of the ports IB or I8, while connecting the other port I8 or I6, respectively, through the chamber l5 in the D-valve 'Ill with the exhaust port Il', The spring I2 pressing between its seats l2 and 'i4 maintains the D-valve in either of its end positions, since the seat 'I4 is mounted centrally of the two positions for the D-valve, so that the spring I2 is biased either to one side or the other of the center line between the recess 'I4 and the exhaust port I'I.

The detailed description to this Point, except possibly for the addition of spring l2 is conventional for all slow acting reciprocating expansible chamber` motors of the piston and cylinder type. Accordingly the valve mechanism of this invention, which description will follow, can be readily adapted to the conventional type of D-valve controlled reciprocating expansible chamber type motor without requiring a new design for the cylinder or for the D-valve provided for controlling the reciprocation of the piston in the cylinder. The following description is now related to the new features of the valve mechanism which are the essential elements of the present invention.

3. Automatic D-valve control mechanism The particular chest BI) shown in the present embodiment of this invention comprises a central rectangular chamber 65 having at each end a control cylinder and 8|, each control cylinder being parallel with the slide path of the D-valve and on opposite sides of the D-valve. Herein these control cylinders may be drilled into solid portions in the chest block at each end of the chamber 65, and vhave diagonally their outer ends capped with plugs 82 and 83, respectively, acting as cylinder heads; These cylindrical holes stop or may be drilled short of the edge of the chamber 65 to provide shoulders 8.0 and 85, and then'holes or apertures 86 and 81 oi reduced diameter, axially with the control cylinders 80 and 8|, may extend through to the chamber 65. Aligned with each of the axes of the control cylinders 80 and 8| at the opposite ends of the chamber 05 may be control piston guides such as smaller holes 88 and 89 which may pass clear through the housing block 60 and be closed by suitable plate members 90 and 9|, respectively.

Mounted in each control cylinder and 8i is valve control pistons |00 and |0| which are limited from contacting the ends lof the cylinders 80 and 8| by reduced diameter abutments |02 and |03, one at each end of piston 00, and similar abutment-s |04 and |05 one at each end of piston |0|. The abutments |03 and |05 thus contact the shoulders 84 and 85 so that the pistons |00 and |0| will not close exhaust ducts |06 and |01, respectively, at the inner `end of the cylinders 80 and 8|. These exhaust ducts |06 and |01 may be open to the atmosphere and permit unrestricted movement of the control pistons |00 and |0|. The other abutments |02 and |04 at the opposite ends of the pistons |00 and |0| may Contact the ends of the plugs 82 and 83, respectively, so that the pistons |00 and |0| will not close the inlet ducts |08 and |09 which ducts may be drilled radially outwardly from the cylinders 80 and 8| to the surface of chest 60 engaging the flat surface I2 of the cylindrical housing I0.

Cooperating with the open outer ends of the ducts |08 and |09 there are provided an additional pair of ducts ||4 and ||5 which may be drilled at an angle into the main cylinder housing |0 so that they will open into the main chamber of the cylinder just behind the piston 50 when it is at the corresponding end of the cylinder, as shown in Fig. 2. These ducts H4 and thus connect the outer ends of the control cylinders 80 and 8| for the D-valve control mechanism with the chamber of the reciprocating motor, so that said D-valve control pistons are controlled by the pressure in the main cylinder chamber l. Thus the drilled ducts H4 and ||5 are the only changes which need be made in a standard cylinder housing for a recip- CII rocating expansible chamber motor of the type Y above described for which the present valve mechanism of this invention is adapted.

inwardly from the control pistons |00 and I0! are reduced piston sections ||8 and H9 of smaller diameter than the abutments |00 and |05, which sections ||8 and I9 extend through the reduced apertures 86 and 8l at the inner ends of the cylinders 00 and 8| communicating with the chamber 65. It is desirable that the iit between the control pistons |00 and |0| "and their chambers 80 and 8| be as snugas possible and still permit easy sliding, as well as the rit between the reduced piston sections |8 and |9 and their corresponding apertures 86 and 91, so as to prevent as much uid leakage as possible. The length of the sections H8 and ||9 should be a little longer than the distance of the stroke of the pistons |00 and |0| in the cylinders 80 and 8|, so as to provide sucient space for the mounting of the remaining part of the valve control mechanism connected to these pistons.

Extending axially inwardly from the shoul- 6. ders|28 and |29 atthe end of the reduced por-v tions ||8 and ||9, are control piston rods |30 and |3| of still further reduced diameter, which rods may .extend the `remainder of the length across the chamber 65 and into the guide holes 88 and 89, respectively, at the opposite ends of the chest 60 for a distance greater than the length of the stroke of said pistons. For a distance greater than the depth of the guide holes 88 and`89, the piston rods |30 and |3| have longitudinal slots |32 and |33 extending from their ends so that the pressure of the iluid in the chest 65 will be the same inside the holes 68 and 89 as in the chest and no restriction of movement of said pistons will occur due to compression or expansion of uid in the end portion of the holes 88 and 89.

Spaced from the shoulders |28 and 29 between the ends of the control piston sections ||8 and ||9 and the control piston rods |30 and |3|, are slide guide collars |40 and |4I, respectively; which are keyed to the piston rods and |3|, Such as by means of pins |42 and |03. These guide collars slide along the sides |44 and |05, respectively, of the side Walls of chamber 85 as shown in Figs. 1, 3, 4, 5 and 6, so as to prevent turning of the pistons and piston rods |30 and |3 I, as well as to prevent any bending oi the rods in the chamber 65.

Spaced from the collars and |4| and extending lengthwise along the rods |30 and |3| are parallel cams and |5| which project above the upper surfaces of the rods |30 and |3| so as to Cooperate with the ends of the pivoted lever arms and |6|, pivoted on the rods |30 and |3| between the guide members |40 and |4| and the shoulders of the end of the reduced Sections ||8 and |9 of the control pistons, respectively. These cams |50 and 5| have a length about equal to the space between these shoulders |28 and |29 and the guide collar |40 and Uil and have ends sloping toward the upper surface of said rods along which the ends of the levers |60 and |6| may easily ride. The height of the cams |50 and |5| is suiicient to lift the arms |60 and |6| clear of the top ofthe D-valve 'l0 as Will be described later and as shown in Fig. fl.

rEhe lever arms |60 and |6| pivoted, respectively, on the piston rods Y|30 and |3|, are permitted slight axial movement along the length ofthe piston rods between the shoulder |28 and collar |40 along the .rod |30, and between the shoulder |29 and the collar HH along the rod i3 i.

-The levers |60 and |6| may be urged toward the stops |40 and |4| by means of helical springs |64 and |65, one end of which springs may be anchored in a hole or suitable aperture in the piston sections ||8 and ||9, and the other end of which springs may be bent over the top oi the lever arms |60 and |6|, respectively. These springs thereby'not only urge the lever arms |60 and |6| away from the shoulders |28 and |29 and against collars |40 and |4l, but also maintain the lever arms |60 and |6| riding along and in Contact with upper surfaces and cams |50 and |5| on the piston rods 3| and |30, respectively. Thus the lever arms |60 and |6| extend across the substantial width of the chamber 65 from one parallel control piston rod to the other. Intermediate of the lever arms |60 and |6| there may be dependent sections |66 and |61 (see Figs. 3 and 4) respectively, which engage opposite ends of the D-valve 10, so that as the pistons |00 and |0| are moved they will also move the D-valve '10, as will be described below in the operation of this device. The helical springs |64 and |65 are anchored into the piston sections H8 and H0 at a distance sufficient from the abutments |03 and |05, so as not to hit against the end side of the chamber 65, when said piston sections H8 and H9 are retracted in their respective control cylinders.

The uid pressure supply for the chest and the operation of the reciprocating motor and main piston 50 in the main cylinder I0 may be provided through a duct |60, which may be connected to a fluid pressure supply pipe 8| connected into the side or other suitable portion of the chest 60.

The types of bolts and structures and ducts shown in the drawings may be substituted for any type of tappings and tubes for eiectively connecting the essential parts described without departing from the scope of this invention. For example, the control cylinders 80 and 8| and their piston guides 88 and 80 may be separate pieces of material instead of being drilled out of a valve chest housing block as shown herein.

II. OPERATION OF THE VALVE CONTROL MECHANISM Referring first to the positions shown in Figs. 1 and 2, the main motor piston 50 is shown toward the left end of the main motor cylinder. For the purpose of describing this operation let us assume that this piston has just been pushed to this end from the right end of the cylinder by pressure in the chamber H which has been introduced through the intake duct |8| into chamber 65 and thence through the uncovered port of the D-valve mechanism and through ducts 23 and 3| into the chamber H. As soon as the piston 50 reaches the position shown in Fig. 2, the opening to the duct H5 at the left end of the cylinder is uncovered so that the pressure from inside the chamber also passes through the ducts H5 and |09 into the small control cylinder 8| of the control piston |0|. Thus the iuid pressure in chamber H, is transmitted to the side of the piston having the larger eiective area, since the other side of the piston has an area reduced to end area of piston section |29 and the end of the piston rod |3| inside the chamber 65, Because of the difference in effective areas the control piston |0| is then pushed towards the right from the position shown in Fig. 1

The control piston |0| on its travel towards the right moves with its piston portion H9, piston rod ISI, guide collar |4| and the lever arm |B|. During the rst part of its movement, the outer end of the lever arm |6| rides over the cam |50 on the opposing control piston rod |30, and falls down on the upper rod surface as shown in Fig. 5, so that the lower edge |61 of lever arm |6| (see Fig. 3) engages the left end of the D- valve 10.

Further movement of the piston |0| then compresses the spring |65 on the piston section H6, so that the lever |6| slides axially along the piston rod |3| into engagement with. the shoulder |26. Simultaneously, with this portion of the movement compressing spring |65, the cam on the piston |3| raises the lever arm 60, pivoted on the opposing control piston rod |30, above the top surface of the D-valve as shown in Fig. 4. Then the action of the compressed spring |64 on piston section H8 slides the lever arm |60 toward the stop |40, causing the bottom edge |66 of the lever arm |60 to slide over and ride on 8 the top of the D-valve '|0, holding the outer end of the lever |60 away from further contact with the cam 5| or With the upper surface of the piston rod |3|, thereby preventing the lever arm |60 with its pushing projection |66 from obstructing movement of the D-valve toward the right.

Since the ducts |08 and H4 from the piston chamber are connected to the pressure chamber I|, the control piston |00 maintains the D- valve in the position shown in Fig. 1 during the entire stroke of the motor piston 50 from the right to the left. Therefore it is necessary for the action of the cam |5| on the rod |30 of the control piston |0| to lift the lever |60 from the end of the D-valve 10 as shown in Fig. 4, so that the pressure operating on control piston |0| moving it towards the right will not be stopped by an equal counterpressure in the control cylinder 80 upon the control piston |00.

Now further movement of the piston |0| toward the right slides the D-valve 10 into the position shown in Fig. 6 at the right end of its recess I4, with the lever arm |60 still riding on the top of the D-valve 10. Since the position shown in Fig. 6 is to the right of the central position for the spring '|2 acting against the top of the D-valve, the spring T2 will now be on the other side of its center position and aid in maintaining the D-valve 10 in the position shown in Fig. 6 until it is again to be pushed back into the position shown in Fig. 1 by later operation of the control piston |30 and its lever arm |60.

Before the lever arm |60 can be operated to push the D-valve 10 back to the left, it must be retracted to the right beyond the right end of the iD-valve. This is accomplished as soon as the chamber behind the motor piston 50 in the main motor cylinder, is connected by the D-valve through the ducts 3| and 23 and chamber 'l5 to the exhaust port and duct 22. Thus the pressure which has now built up in the chamber is exhausted and the pressure of the fluid in the chamber 65 is now permitted to flow through port I6 and ducts 2| and 36 to the left side of the motor piston 50 pushing the motor piston back to its right end position. This is the case when the D-valve is in the position shown in Fig, 5. Thus, as soon as the exhaust is connected to the control cylinder 80 through the ducts |06 and i i4 and chamber i, and then through ducts 3| and 23 and D-valve chamber 15 to exhaust ducts 22 and 25, the pressure within the chamber 30 is reduced materially less than that within the charnber 65 so that the pressure on the shoulder |23 and the end of control piston |30 through slot |62 will move the control piston |00 from the position shown in Fig. 1 back to its extreme right end of the control cylinder 80, corresponding to the position of control piston |0| in Fig. 1. This movement also retracts the lever |60 `against collar |40. This retraction of the cylinder |00 takes place during the last part of the movement of the main motor piston 50 from the position shown in Fig. 2 to the dotted line position |60 at the right end of the motor cylinder.

Now the same cycle described above for control piston |0| can take place for the control piston 00, to move the motor piston back to the left end of the motor cylinder as shown in full lines in Fig. 2. Thus for each reciprocation of the piston 50 in the cylinder chamber H. there is a movement of one of the control pistons |00 or |0| in one direction, and the movement of the other control piston |0| or |00 in the opposite direction, and each of the control pistons |0| and 9. are set for the next operation at the end of each stroke of the motor piston.

IEI. APPLICATIONS Fig. 7 shows a pressure lubricating type system employing a reciprocating motor of the type shown in Figs. 1 through 6 with a control mechanism according to this invention in a fluid control chest 60. The motor and valve control assembly is shown mounted on a suitable bracket 200, which bracketV is connected to a plunger type pump 20| which may be inserted into a container or drum 202 of a suitable grease or other uid 203. The end of the piston rod 52 may be removably connected at 205 to the end of a pump piston rod 206, so that the whole motor and valve assembly may be readily removed from the pump 20| and bracket 200; the bracket 200 being attached to the apertures 4| in anges G0 by suitable fastening means, such as bolts 20'?.

The constant pressure on the motor piston 50 in the motor cylinder I0, thus applies a constant pressure on the fluid being pumped from the container 202 at the outlet port 2 I 0 of the pump 20|. This port may be connected, as shown, through a suitable pressure hose 2|| to a grease gun 2|2, which gun is operated by a suitable valve or trigger 2 |11. As soon as the trigger 2|4 is opened, pressure is relieved on the uid from port 2 0 and the constant pressure being applied by the motor mechanism |0 and piston 50 will immediately force more fluid 203 from the container 202 through the pump 20| out through port 2|!) and the hose 2| through the nozzle 2 5 of the gun 2 I2.

Although the particular system just described is adapted for being operated by compressed air, it can readily be seen that the control valve mechanism of this invention may also be used in cooperation with other fluids, such as steam or even liquids, without departing from the scope of this invention.

The type of reciprocating motor and control valve mechanism of this invention may also be adapted for pumping other fluids besides grease, whether viscous as plastic filling materials, or non-viscous, in that the operation of the control valve mechanism is adapted for reciprocations as slow as anywhere from about one a minute, or even less, up to a speed of about one a second or more. One of the important advantages of the valve control mechanism of this invention is that this mechanism is entirely automatic, and will give a continuous constant pressure on the end of the reciprocating motor piston at all times regardless of the position of the motor piston along its stroke and not get locked on dead center or have to be manually moved at any time.

While there is described above the principles of this invention in connection with specific apparatus it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of this invention.

What is claimed is:

1. A valve mechanism for controlling reciprocations of an expansible chamber motor comprising: a valve chest, a reciprocating valve movable between two positions in said chest, a pair of pressure operated reciprocating parallel pistons in said chest, each piston corresponding and being controlled by a different direction of reciprocation of said motor, pivoted arm means on each said piston for engagement with said valve to effect its movement from one of its positions to the other, and cam means on each said piston to remove the engagement of one of said arm means y1|)` of one piston with said valve when the other piston is shifted to move the other arm means into engagement with said valve.

2. A distributing valve mechanism for controlling reciprocations of an expansible chamber motor, comprising: a pressure iiuid valve chest, a sliding valve having two positions in said chest, a pair of fluid pressure operated reciprocating parallel pistons in said chest, each piston controlling a different direction of reciprocation of said motor, piston rods connected to each of said pistons, a pivoted pusher arm mounted on each said piston rod for engagement with opposite ends in said valve, and cam means on each of said piston rods to disengage the arm on the other piston from the end of said valve when said one piston is moved into engagement with said valve for sliding the same.

3. The valve mechanism of claim 2 wherein the motor has an expansible chamber and said pistons are controlled by the pressure of the fluid operating said motor through ducts communicating with the expan'sible chamber of said motor.

4. A mechanism according to claim 2 including means for maintaining said valve in one position until one of said arms engages it to slide it to its other position.

5. A valve mechanism according to claim fl wherein said means for maintaining said valve in one position comprises a resilient means acting between said valve and the inside of said chest.

6. A valve mechanism according to claim 2 wherein said pivoted pusher arms are axially slidable along said piston rods between xed limits on said rods.

'7. The valve mechanism according to claim 6 including means on each piston rod to urge said pivoted lever arms towards one of said stop limits.

8. A valve mechanism according to claim 6 wherein said xed limits comprise a collar spaced from a shoulder along each said piston rod.

9. A valve mechanism according to claim 8 wherein said collars are provided with guide means to prevent the rotation of said piston rods when said lever pusher arms are pivoted on said piston rods.

10. In an expansible chamber motor having a reciprocating motor piston in a motor cylinder and a fluid pressure valve chest containing a sliding D-valve for controlling the operation of said piston, an automotive D-valve operating mechanism comprising: a pair of parallel reciprocating control pistons in a, pair of control cylinders and control piston rods connected to said control pistons and mounted in said chest, a, pivoted D-valve pushing lever mounted on each control piston rod, a cam on each said rod contacted by the lever pivoted to the other said rod, resilient means to push said levers out of pushing contact with said D-valve when lifted by the cam means of the other said rod thereby releasing the D-Valve for movement by the lever of said other piston rod, and means to operate alternately said control piston rods at each end of the stroke of said piston including ducts connecting said control cylinders to said motor cylinder, which ducts are opened and closed by said motor piston.

11. A distributing valve mechanism for controlling the reciprocations of a piston in a cylinder of an expansible chamber motor, comprising: a iluid pressure Valve chest, a D-valve slidable in said chest between two limited positions, a pair of fluid pressure operated reciprocating parallel control pistons with piston rods mounted in said 1l chest on each side of said D-valve mechanism, each control piston rod in .said chest being provided with a lever arm pivotally mounted thereon for engagement with one end of said D-valve, whereby the operation of one of the control pistons slides said D-valve in one direction and the operation of the other control piston slides the D-valve in the other direction, and cam means mounted on each control piston rod for disengaging said lever arm mounted on the other control piston rod when the lever arm on said one control piston rod is pushing the D-valve.

References Cited in the file of this patent CFI Number UNITED STATES PATENTS Name Date Griln Mar. 1, 1892 Bartholomew Aug. 23, 1892 Lundquist July 21, 1903 Woodcock Mar. 2, 1937 

